Conventionally, within the art of rotating electric machines, a rotating electric machine control system controls at least one rotating electric machines within a vehicle to provide power for a travel of the vehicle.
For example, a patent document 1 (i.e., Japanese patent JP-A-2013-1185) discloses a rotating electric machine control system having a voltage converter for converting a direct current voltage of a direct current power source and outputting a converted three-phase alternating current to the rotating electric machine and a control section for controlling the voltage converter to have an output of a requested torque from the rotating electric machine.
The rotating electric machine control system described above further includes a current detector that detects an electric current output from the voltage converter to the rotating electric machine in each of three phases, a voltage detector that detects the direct current voltage supplied from the direct current power source, and a rotation detector that detects a rotation position of the rotating electric machine. The control section controls the voltage converter based on detection signals from each of those detectors.
However, in view of installability of the rotating electric machine control system within a vehicle, when considering a functionality distribution consideration and a manufacturing cost, the voltage converter and the control section in the rotating electric machine control system may be provided as two separate components, rather than one. More practically and precisely, a power control unit having the voltage converter and a control section may be separated from each other. Further, the rotation detector may also be separately provided apart from the power control unit, to be close to the rotating electric machine.
On the other hand, the current detector detects the electric current that is output from the voltage converter to the rotating electric machine in each of the three phases. When the voltage converter includes a booster converter, the current detector also detects the electric current flowing in a reactor. Therefore, the current detector is arranged to be proximate to the voltage converter.
Further, the voltage detector detects the direct current voltage supplied from the direct current power source. When the booster converter is included in the voltage converter, the voltage detector also detects the direct current voltage after the boosting. Therefore, the voltage detector is also arranged to be proximate to the voltage converter.
Thus, the current detector and the voltage detector constitute the power control unit together with the voltage converter. Therefore, the number of communication lines (i.e., wire harness) connecting the power control unit and the control section increases dramatically. The increase of the number of communication lines means an increase of the manufacturing cost. Further, when the control section is disposed in a vehicle compartment and the power control unit is disposed in an engine room, the communication lines connecting the two have to pass through a dividing wall between the vehicle compartment and the engine room, i.e., pass through a small hole, which has, usually, a very small dimension, for the quietness of the compartment and the rigidity of the vehicle body. That is, the number of communication lines must be limited under a certain number for the above-described restrictions.
For the resolution of the above problem, a communication frame including two or more detection values from at least one of the current detector or the voltage detector may be generated, and such communication frames may be transmitted via the multiplex communication line, for reducing the number of communication lines. This multiplex communication line is used for communications according to a CAN-FD (Controller Area Network Flexible Data Rate) protocol or similar communications (CAN is a registered trademark). In such case, the power control unit further includes a communication device, which receives plural values detected by at least one of the current detector or the voltage detector, and generates and outputs a communication frame which includes plural values from the detectors.
However, the delay of communication caused by a signal transmission via the multiplex communication line will make it difficult to time-synchronize the detection values from the current/voltage detectors with the detection value from the rotation detector. In other words, the controllability of the voltage converter may be deteriorated.